Neuroblastoma is a frequently lethal childhood tumor in which MYC gene deregulation, commonly as MYCN amplification, portends poor outcome. Identifying the requisite biopathways downstream of MYC may provide therapeutic opportunities. We used transcriptome analyses to show that MYCN-amplified neuroblastomas have coordinately deregulated myriad polyamine enzymes (including ODC1, SRM, SMS, AMD1, OAZ2, and SMOX) to enhance polyamine biosynthesis. High-risk tumors without MYCN amplification also overexpress ODC1, the ratelimiting enzyme in polyamine biosynthesis, when compared with lower-risk tumors, suggesting that this pathway may be pivotal. Indeed, elevated ODC1 (independent of MYCN amplification) was associated with reduced survival in a large independent neuroblastoma cohort. As polyamines are essential for cell survival and linked to cancer progression, we studied polyamine antagonism to test for metabolic dependence on this pathway in neuroblastoma. The Odc inhibitor A-difluoromethylornithine (DFMO) inhibited neuroblast proliferation in vitro and suppressed oncogenesis in vivo. DFMO treatment of neuroblastoma-prone genetically engineered mice (TH-MYCN) extended tumor latency and survival in homozygous mice and prevented oncogenesis in hemizygous mice. In the latter, transient Odc ablation permanently prevented tumor onset consistent with a time-limited window for embryonal tumor initiation. Importantly, we show that DFMO augments antitumor efficacy of conventional cytotoxics in vivo. This work implicates polyamine biosynthesis as an arbiter of MYCN oncogenesis and shows initial efficacy for polyamine depletion strategies in neuroblastoma, a strategy that may have utility for this and other MYC-driven embryonal tumors. [Cancer Res 2008;68(23):9735-45]

The mechanisms causing persistence of embryonal cells that later give rise to tumors is unknown. One tumorigenic factor in the embryonal childhood tumor neuroblastoma is the MYCN protooncogene. Here we show that normal mice developed neuroblast hyperplasia in paravertebral ganglia at birth that completely regressed by 2 weeks of age. In contrast, ganglia from MYCN transgenic (TH-MYCN) mice demonstrated a marked increase in neuroblast hyperplasia and MycN expression during week 1. Regression of neuroblast hyperplasia was then delayed and incomplete before neuroblastoma tumor formation at 6 and 13 weeks in homo-and hemizygote mice, respectively. Paravertebral neuronal cells cultured from perinatal TH-MYCN mice exhibited 3-to 10-fold resistance to nerve growth factor (NGF) withdrawal, compared with normal mice. Both low-and high-affinity NGF receptors were expressed in perinatal neuroblast hyperplasia but not in neuroblastoma tumor tissue. MYCN transgene amplification was present at low levels in perinatal neuroblast hyperplasia from both homoand hemizygote TH-MYCN mice. However, only in hemizygous mice did tumor formation correlate with a stepwise increase in the frequency of MYCN amplification. These data suggest that inappropriate perinatal MycN expression in paravertebral ganglia cells from TH-MYCN mice initiated tumorigenesis by altering the physiologic process of neural crest cell deletion. Persisting embryonal neural crest cells underwent further changes, such as MYCN amplification and repression of NGF receptor expression, during tumor progression. Our studies provide a model for studying perinatal factors influencing embryonal tumor initiation.neuroblastoma ͉ regression ͉ in vivo model

The N-Myc oncoprotein is a critical factor in neuroblastoma tumorigenesis which requires additional mechanisms converting a low-level to a high-level N-Myc expression. N-Myc protein is stabilized when phosphorylated at Serine 62 by phosphorylated ERK protein. Here we describe a novel positive feedback loop whereby N-Myc directly induced the transcription of the class III histone deacetylase SIRT1, which in turn increased N-Myc protein stability. SIRT1 binds to Myc Box I domain of N-Myc protein to form a novel transcriptional repressor complex at gene promoter of mitogen-activated protein kinase phosphatase 3 (MKP3), leading to transcriptional repression of MKP3, ERK protein phosphorylation, N-Myc protein phosphorylation at Serine 62, and N-Myc protein stabilization. Importantly, SIRT1 was up-regulated, MKP3 down-regulated, in pre-cancerous cells, and preventative treatment with the SIRT1 inhibitor Cambinol reduced tumorigenesis in TH-MYCN transgenic mice. Our data demonstrate the important roles of SIRT1 in N-Myc oncogenesis and SIRT1 inhibitors in the prevention and therapy of N-Myc–induced neuroblastoma.

Resistance of normal cells to tumour necrosis factor related apoptosis inducing ligand (TRAIL) induced apoptosis is believed to be mediated by expression of two decoy receptors. Here we show that the expression and localisation of TRAIL receptors (TRAIL-Rs) vary between different cells and that resistance to TRAIL is mediated by different mechanisms. The decoy receptor, TRAIL-R3, appeared important in protection of endothelial cells, whereas lack of surface death receptor expression and as yet unknown intracellular inhibitor(s) of apoptosis downstream of caspase-3 may play a major role in protection of melanocytes and fibroblasts from TRAIL induced apoptosis, respectively. Differential subcellular location of decoy receptors may be an important determinant of their effectiveness in different types of normal cells. ß

Previous studies have shown that activation of NF-κB can inhibit apoptosis induced by a number of stimuli. It is also known that TNF-related apoptosis-inducing ligand (TRAIL) can activate NF-κB through the death receptors TRAIL-R1 and TRAIL-R2, and decoy receptor TRAIL-R4. In view of these findings, we have investigated the extent to which activation of NF-κB may account for the variable responses of melanoma lines to apoptosis induced by TRAIL and other TNF family members. Pretreatment of the melanoma lines with the proteasome inhibitor N-acetyl-l-leucinyl-l-leucinyl-l-norleucinal (LLnL), which is known to inhibit activation of NF-κB, was shown to markedly increase apoptosis in 10 of 12 melanoma lines with death receptors for TRAIL. The specificity of results for inhibition of NF-κB activation was supported by an increase of TRAIL-induced apoptosis in melanoma cells transfected with a degradation-resistant IκBα. Furthermore, studies with NF-κB reporter constructs revealed that the resistance of melanoma lines to TRAIL-induced apoptosis was correlated to activation of NF-κB in response to TRAIL. TRAIL-resistant sublines that were generated by intermittent exposure to TRAIL were shown to have high levels of activated NF-κB, and resistance to TRAIL could be reversed by LLnL and by the superrepressor form of IκBα. Therefore, these results suggest that activation of NF-κB by TRAIL plays an important role in resistance of melanoma cells to TRAIL-induced apoptosis and further suggest that inhibitors of NF-κB may be useful adjuncts in clinical use of TRAIL against melanoma.

The family of tripartite-motif (TRIM) proteins are involved in diverse cellular processes, but are often characterized by critical protein–protein interactions necessary for their function. TRIM16 is induced in different cancer types, when the cancer cell is forced to proceed down a differentiation pathway. We have identified TRIM16 as a DNA-binding protein with histone acetylase activity, which is required for the retinoic acid receptor β2 transcriptional response in retinoid-treated cancer cells. In this study, we show that overexpressed TRIM16 reduced neuroblastoma cell growth, enhanced retinoid-induced differentiation and reduced tumourigenicity in vivo. TRIM16 was only expressed in the differentiated ganglion cell component of primary human neuroblastoma tumour tissues. TRIM16 bound directly to cytoplasmic vimentin and nuclear E2F1 in neuroblastoma cells. TRIM16 reduced cell motility and this required downregulation of vimentin. Retinoid treatment and enforced overexpression caused TRIM16 to translocate to the nucleus, and bind to and downregulate nuclear E2F1, required for cell replication. This study, for the first time, demonstrates that TRIM16 acts as a tumour suppressor, affecting neuritic differentiation, cell migration and replication through interactions with cytoplasmic vimentin and nuclear E2F1 in neuroblastoma cells.

Past studies have shown that TNF-related apoptosis-inducing ligand (TRAIL) induced apoptosis in a high proportion of cultured melanoma by caspase-dependent mechanisms. In the present studies we have examined whether TRAIL-induced apoptosis of melanoma was mediated by direct activation of effector caspases or whether apoptosis was dependent on changes in mitochondrial membrane potential (MMP) and mitochondrial-dependent pathways of apoptosis. Changes in MMP were measured by fluorescent emission from rhodamine 123 in mitochondria. TRAIL, but not TNF-α or Fas ligand, was shown to induce marked changes in MMP in melanoma, which showed a high correlation with TRAIL-induced apoptosis. This was associated with activation of proapoptotic protein Bid and release of cytochrome c into the cytosol. Overexpression of B cell lymphoma gene 2 (Bcl-2) inhibited TRAIL-induced release of cytochrome c, changes in MMP, and apoptosis. The pan caspase inhibitor z-Val-Ala-Asp-fluoromethylketone (zVAD-fmk) and the inhibitor of caspase-8 (z-Ile-Glu-Thr-Asp-fluoromethylketone; zIETD-fmk) blocked changes in MMP and apoptosis, suggesting that the changes in MMP were dependent on activation of caspase-8. Activation of caspase-9 also appeared necessary for TRAIL-induced apoptosis of melanoma. In addition, TRAIL, but not TNF-α or Fas ligand, was shown to induce clustering of mitochondria around the nucleus. This process was not essential for apoptosis but appeared to increase the rate of apoptosis. Taken together, these results suggest that TRAIL induces apoptosis of melanoma cells by recruitment of mitochondrial pathways to apoptosis that are dependent on activation of caspase-8. Therefore, factors that regulate the mitochondrial pathway may be important determinants of TRAIL-induced apoptosis of melanoma.

IntroductionKnee osteoarthritis is associated with persistent joint pain, stiffness, joint deformities, ligament damage, and surrounding muscle atrophy. The complexity of the disease makes treatment difficult. There are no therapeutic drugs available to halt the disease progression, leaving patients dependent on pain medication, anti-inflammatory drugs, or invasive joint replacement surgery.Case presentationsFour patients with a history of unresolved symptomatic knee osteoarthritis were investigated for the therapeutic outcome of combining an exercise rehabilitation program with intra-articular injections of autologous StroMed (ie, stromal vascular fraction cells concentrated by ultrasonic cavitation from lipoaspirate) and platelet-rich plasma (PRP). The Knee Injury and Osteoarthritis Outcome Score questionnaire (KOOS) was administered along with physical function tests over a 12-month period. The first patient achieved a maximum therapeutic outcome of 100 in all five KOOS subscales (left knee), and 100 for four subscales (right knee). The second patient scored 100 in all five KOOS subscales (left knee), and greater than 84 in all subscales (right knee). Treatment of the third patient resulted in improved outcomes in both knees of >93 for four KOOS subscales, and 60 for the Function in Sport and Recreation subscale. The fourth patient improved to 100 in all five KOOS subscales. In all patients, the physical function “Get-up and Go” test and “Stair Climbing Test” returned to normal (a value of zero).ConclusionThis case series indicates that improved outcomes may be obtained when autologous stromal vascular fraction (StroMed) cell therapy is combined with traditional exercise practices and PRP for osteoarthritis. Of the seven joints treated: all patients’ scores of pain improved to >96; and quality of life scores to >93. Functional performance measures of mobility returned to normal. This simple treatment appears to be extremely effective for osteoarthritis disorders that have no drug treatment to halt disease progression.